Smart cards are used as bankcards, ID cards, telephone cards and the like. They are based upon the use of an electromagnetic coupling (either by direct physical contact or by electromagnetic waves) between a smart card's electronic components and a card reader, pickup head, etc. of a receiving device such as an ATM machine. These electrical couplings may be used to effect a reading mode alone or a read/write mode.
Smart cards are usually made by assembling several layers of plastic sheets in a sandwich array. In the case of "contact" type smart cards, the card's contact surface is placed in direct physical contact with a machine's reader or pickup head component. In the case of so-called "contactless" smart cards (i.e., those smart cards whose electronic components are accessed by electromagnetic waves rather than by physical contact), a center layer of a polymerizable resin totally encapsulates an electronic module that may, for example, comprise an IC chip that is connected to an inductive coil type antenna that is capable of receiving electromagnetic waves through the body of the card.
The methods for making smart cards have varied considerably. For example, European Patent 0 350 179 discloses a smart card wherein electronic circuitry is encapsulated in a layer of plastic material that is introduced between the card's two surface layers. The method further comprises abutting a high tensile strength holding member against a side of a mould, locating the smart card's electronic components with respect to that side and then injecting a reaction moldable polymeric material into the mould such that it encapsulates the electronic components.
European Patent Application 95400365.3 teaches a method for making contactless smart cards. The method employs a rigid frame to position and fix an electronic module in a void space between an upper thermoplastic sheet and a lower thermoplastic sheet. After the frame is mechanically affixed to the lower thermoplastic sheet, the void space is filled with a polymerizable resin material.
U.S. Pat. No. 5,399,847 teaches a credit card that is comprised of three layers, namely, a first outer layer, a second outer layer and an intermediate layer. The intermediate layer is formed by injection of a thermoplastic binding material that encases the smart card's electronic elements (e.g., an IC chip and an antenna) in the intermediate layer material. The binding material is preferably made up of a blend of copolyamides or a glue having two or more chemically reactive components that harden upon contact with air. The outer layers of this smart card can be made up of various polymeric materials such as polyvinyl chloride or polyurethane.
U.S. Pat. No. 5,417,905 teaches a method for manufacturing plastic credit cards wherein a mold tool comprised of two shells is closed to define a cavity for producing such cards. A label or image support is placed in each mold shell. The mold shells are then brought together and a thermoplastic material injected into the mold to form the card. The inflowing plastic forces the labels or image supports against the respective mold faces.
U.S. Pat. No. 5,510,074 teaches a method of manufacturing smart cards having a card body with substantially parallel major sides, a support member with a graphic element on at least one side, and an electronic module comprising a contact array that is fixed to a chip. The manufacturing method generally comprises the steps of: (1) placing the support member in a mold that defines the volume and shape of the card; (2) holding said support member against a first main wall of the mold; (3) injecting a thermoplastic material into the volume defined by the hollow space in order to fill that portion of the volume that is not occupied by the support member; and (4) inserting an electronic module at an appropriate position in said thermoplastic material before the injected material has the opportunity to completely solidify.
U.S. Pat. No. 4,339,407 discloses an electronic circuit encapsulation device in the form of a carrier having walls which have a specific arrangement of lands, grooves and bosses in combination with specific orifices. The mold's wall sections hold a circuit assembly in a given alignment. The walls of the carrier are made of a slightly flexible material in order to facilitate insertion of the smart card's electronic circuitry. The carrier is insertable into an outer mold. This causes the carrier walls to move toward one another in order to hold the components securely in alignment during the injection of the thermoplastic material. The outside of the walls of the carrier have projections thereon which serve to mate with detents on the walls of the mold in order to locate and fix the carrier within the mold. The mold also has holes to permit the escape of trapped gases.
U.S. Pat. No. 5,350,553 teaches a method of producing a decorative pattern on, and placing an electronic circuit in, a plastic card in an injection molding machine. The method comprises the steps of: (a) introducing and positioning a film (e.g., a film bearing a decorative pattern), over an open mold cavity in the injection molding machine; (b) closing the mold cavity so that the film is fixed and clamped in position therein; (c) inserting an electronic circuit chip through an aperture in the mold into the mold cavity in order to position the chip in the cavity; (d) injecting a thermoplastic support composition into the mold cavity to form a unified card; and (e) thereafter, removing any excess material, opening the mold cavity and removing the card.
U.S. Pat. No. 4,961,893 teaches a smart card whose main feature is a support element that supports an integrated circuit chip. The support element is used for positioning the chip inside a mold cavity. The card body is formed by injecting a plastic material into the cavity so that the chip is entirely embedded in the plastic material. In some embodiments, the edge regions of the support are clamped between the load bearing surfaces of the respective molds. The support element may be a film which is peeled off the finished card or it may be a sheet which remains as an integral part of the card. If the support element is a peel-off film, then any graphics element(s) contained therein are transferred and remain visible on the card. If the support element remains as an integral part of the card, then such graphic(s) elements are formed on a face thereof and, hence, are visible to the card user.
U.S. Pat. No. 5,498,388 teaches a smart card device that includes a card board having a through opening. A semiconductor module is mounted onto this opening. A resin is injected into the opening so that a resin molding is formed under such condition that only an electrode terminal face for external connection of said semiconductor module is exposed. The card is completed by mounting a card board having a through opening onto a lower mold of two opposing molding dies, mounting a semiconductor module onto the opening of said card board, tightening an upper die that has a gate leading onto a lower die and injecting a resin into the opening via the gate.
U.S. Pat. No. 5,423,705 teaches a disc having a disc body made of a thermoplastic injection molded material and a laminate layer that is integrally joined to a disc body. The laminate layer includes an outer clear lamina and an inner white and opaque lamina. An imaging material is sandwiched between these lamina.
All of these prior art methods for making smart cards are to some degree concerned with properly positioning and fixing electronic components, modules or assemblies inside the smart card. If the electronic components are not properly affixed they will be moved to random positions when a thermoplastic material is injected into a card-forming, or card core-forming, cavity under the influence of rather high thermoset material injection pressures. The prior art noted above reveals use of various solid holding members such as frames or supports that are often used to position and fix the electronic elements during the thermoplastic injection processes. The use of relatively large, mechanical holding devices having hard, sharply defined, bodies to hold electronic components in place during injection of such thermosetting materials has, however, created certain problems. For example, the bodies of these relatively large holding devices (i.e., large relative to the electronic components they hold) are often adversely effected by those shock, flexure and/or torsion forces the card may encounter in normal (and abnormal) use. In order to minimize the damage caused by such forces, the electronic components held by some of these hard, sharply defined bodies are often positioned in a corner of such smart cards. This positioning limitation usually cuts down on the size and number of electronic components that can be placed in such cards.
Moreover, due to differences in the coefficient of expansion of the materials used to make these relatively large holding devices--relative to the coefficient of expansion of the other elements of such cards--deformations often appear on the external surfaces of finished cards that contain such electronic component holding devices. That is to say that surface deformations can result from the mere presence of such holding members in the body of the card as it experiences different temperatures and pressures during its manufacture. Such deformations are, at best, unsightly; at worst, they may even prevent the card from lying completely flat in the card-receiving receptacles in certain card reading machines.
Some smart card manufacturers have dealt with this problem by reducing the size and/or body of such holding devices by using various glues (rather than mechanical interconnecting locking devices) to securely position their holders (and hence the electronic component that they hold) in their card-forming cavities during the thermoplastic injection process. The use of such glues to secure these holder devices has, however, produced another set of problems. Such problems usually revolve around the fact that most commercially available, fast curing glues that are used to fix such electronic component holders in place also are often characterized by their high degrees of shrinkage. Moreover, relatively large volumes of glue are needed to fix these relatively large holders when they are impinged upon by the incoming thermoset material. Use of the relatively large volumes of high shrinkage glues needed to fix these holders in place tends to wrinkle and otherwise deform the region of a plastic sheet or layer to which such glues are applied. Worse yet, the forces created by these wrinkle-like deformations on the inside surfaces of the plastic sheets (e.g., sheets of polyvinyl chloride) used to make a smart card's surface layer(s) are transmitted through the relatively thin (e.g., from about 0.075 to about 0.25 mm) bodies of these sheet materials. These forces often cause the outer surface of the smart card to take on a local wave-like, bent, or even wrinkled, character. Beyond certain tolerances, these wave-like, bent, or wrinkle-like deformations are unacceptable to the smart card industry. Hence, many techniques have been developed to try to at least minimize deformities of this kind. Unfortunately, such deformations continue to be a problem--especially when smart cards are made using various high speed gluing methods to glue these relatively large holder devices to the thin sheets of the plastic materials (e.g., PVC) that form the outside surfaces of most smart cards.
In further response to the absence of a completely satisfactory solution to the above-noted problems, it has been proposed that both the large, rigid, circuitry holding devices, and the rigid, metal, electronics components (e.g., metal antenna loops, computer chips, capacitors, etc.) that they anchor in place, be replaced with a relatively thin, film-like layer of those polymeric, thermoset adhesive materials that also have the rather unusual ability to act as an electrical conductor. By using such a material, a smart card's circuitry can be made (e.g., by etching) an integral part of the conductive, film-like material. These polymeric, electricity-conducting materials are sometimes referred to as isotropic thermoset adhesive ("ITA") materials.
They were originally developed and used to bond electrical leads to computer chips and thereby eliminate the need for so-called, "gold bump" bonding of such elements. In other words these ITA materials were used to lower electronic component assembly costs by replacing gold as the electrically conductive bonding material used to connect a computer chip and an electrical lead.
These ITA materials were subsequently made into thin, film-like materials in which electrical circuitry was incorporated (e.g., by etching electrical circuitry into the ITA). These ITA film-like materials have been produced by Phillips Electronics, the Netherlands. Aside from their lower space requirements in a smart card, and their lower costs, these ITA films are further characterized by the fact that they are much more flexible than the prior art metal circuitry that the ITA material has sought to replace. Hence, ITA circuits can withstand far greater flexure and/or torsional forces without breaking the electrical flow paths defined by their circuits.
Unfortunately, there is a very severe drawback associated with the use of these film-like materials for smart card circuitry. They lack "body" and mechanical "rigidity" and are, therefor, not well suited to some physical aspects of the manufacturing processes used to make smart cards. For example, these film-like materials usually do not have enough rigidity to be properly handled, and hence properly located in a void space formed by two sheets of thermosetting material that respectively form the top or face surface of the smart card and the bottom or obverse surface of that card. In the practice of the prior art, these ITA film-like materials are placed in this void space and held by the clamping action of the jaw, lip or edge surfaces of the front portions of the opposing molds used to make such cards. In effect, when this holding technique is employed, the front portion of the ITA film is gripped by the front of the mold device and the rear portion of ITA film simply "sags down" in the void space until it comes to rest on the top surface of the bottom layer of the smart card.
Thereafter, a hot, liquid thermosetting polymeric material is injected into the void space. In its sagged down position, the ITA film tends to become embedded in the lower portions of the thermosetting polymeric material that forms the core or center region of the card. For electrical signal transfer reasons, it is, however, highly preferred that the ITA material have a substantially level or horizontal orientation in the core of the card. When the above noted jaw-like clamping action is employed, the ITA film may also take on a "wave-like" configuration under the influence of the rush of incoming liquid, polymeric material. Indeed, the thin film-like ITA material is often torn from its front moorings (provided by the mold's jaw gripping action) by this rush of incoming liquid thermosetting polymeric material. Hence, in spite of all their potential advantages, ITA materials are not normally used as the circuit-defining component of smart cards.